In view of the growing emphasis on renewable energy, increasing amount of biodiesel is produced as an alternative fuel. Biodiesel production through triglyceride transesterification generates about 10 wt % of glycerol as the main byproduct. The growing biodiesel production will lead to large surpluses of glycerol and will impact the current glycerol market notably. It was expected that approximately 37 billion gallons of biodiesel will be produced by 2016, and therefore approximately 4 billion gallons of crude glycerol will be generated. With the expansion of biodiesel production, the prices for both refined glycerol and crude glycerol have plummeted to less than half of that few years ago and will decrease further. It is imperative to find more uses for the over supplied glycerol, which will be of great importance for the biodiesel economy.
Potentially, the bio-generated glycerol can serve as a platform chemical for the synthesis of value-added products. One such product is acrylic acid (AA), which can be industrially produced from the gas phase oxidation of crude oil-based propene and is used primarily for the large volume production of polyacrylates. The large market demand makes acrylic acid one of the most sought after chemicals from biomass resources. The most known way to produce acrylic acid from glycerol is a two-step tandem reaction (FIG. 1). Glycerol is first dehydrated to acrolein over an acid catalyst, and then oxidized to acrylic acid in the second step. Although up to 90% acrolein yield could be achieved from glycerol dehydration in the first step, most of the acid catalysts suffer from fast deactivation due to heavy coke deposition which is inevitably caused by the acidic nature of the catalysts and the high reaction temperature. There have also been reports on direct oxidehydration conversion of glycerol to acrylic acid over bifunctional catalysts. However, the selectivity to acrylic acid is normally lower than 50%, with catalyst deactivation as a severe problem. Thus, from a practical application point of view, the catalyst stability remains a critical issue for the current dehydration-oxidation route or the direct oxidehydration route.
There is a need to provide a method for synthesizing an alkenoic acid such as acrylic acid that overcomes, or at least ameliorates, one or more of the disadvantages described above.